Chemical lift‐off process for nitride LEDs from an Eco‐GaN template using an AlN/strip‐patterned‐SiO₂ sacrificial layer

Abstract

In this research, a nitride light‐emitting diode (LED) fabricated on an electroplated Cu substrate can be removed from a GaN/sapphire (Eco‐GaN) template by conducting the chemical lift‐off (CLO) process using an AlN/strip‐patterned‐SiO2 intermediate sacrificial layer. The regrowth GaN epilayer deposited on AlN/patterned SiO2/Eco‐GaN can achieve a high crystal quality via the epitaxial lateral overgrowth process. To etch the patterned SiO2 and AlN layers, the HF and 80 °C‐KOH solutions were used, respectively. Due to the use of low‐temperature KOH solution, the GaN epilayer would suffer less damage during the CLO process, improving the reuse feasibility for the Eco‐GaN template. Moreover, when the etching treatment was used for the AlN layer, a highly lateral etching rate of 0.5 mm h−1 was achieved. Compared to the conventional LED, the vertical‐type LED/Cu substrate had a higher output power of 212 mW (at 350 mA). Based on our estimation, the output power of LED prepared on Cu substrate had an 86% improvement in comparison to that of conventional LED. Obviously, the good optoelectronic performance of the LED/Cu device can be obtained after performing the CLO process. Furthermore, the separated Eco‐GaN template has high potential for reuse applications, indicating that this technique is helpful to the cost‐effective LED fabrication.

Vertical‐Type Blue Light Emitting Diode by Mixed‐Source Hydride Vapor Phase Epitaxy Method

“…The growth of the 170‐µm‐thick n‐type GaN:Si layer at 1090 °C and 0.7 µm min −1 from the mixed‐source (Ga + Si) contained in the second boat progresses. Figure (e) and (f) show the schematic drawing and SEM image, respectively, of the epilayer connected by the trapezoidal pillar arms grown along the direction originating from the top of the n‐type GaN pyramids with increasing the growth time in the growth of the 170‐µm‐thick n‐type GaN:Si layer. The scale bar is 20 µm.…”

“…A vertical‐type LED with one electrode on each side by metallization on both the upper and bottom sides of the single chip can be obtained by detaching from the substrate using a laser lift‐off (LLO) or a chemical lift‐off (CLO) method in the chip fabrication process and by direct growth of epilayer on Si, SiC, GaN, or GaAs substrates, respectively. These vertical‐type LEDs have higher efficiencies than that of lateral‐type ones because of several advantages such as i) a low operation voltage due to a very low serial resistance, ii) excellent heat dissipation due to high thermal conductivity, iii) good assurance by uniform light emission, and iv) elimination of electrostatic discharge . The LED hybrid technology obtained by adding the packaging steps to emit light also has problems such as an increment in the production cost.…”

Nanostructured Light-Emitters

“…As mentioned above, the laser lift-off technique is one way to fabricate vertical structure LEDs, but will lead to additional defects and a rough surface to devices resulting from the high energy laser irradiation [40][41][42], while chemical lift-off will not damage the interface between epilayer and substrate [43]. Recently, researches have been carried out for chemical lift-off of GaN using various interlayers [43][44][45][46][47][48]106,107,[114][115][116][117][118][119][120]. Lin et al demonstrated the CLO process of InGaN-based LEDs grown on triangle-shaped and truncated-triangle-striped patterned sapphire substrates employing AlN as a sacrificial layer [115,116].…”

Epitaxy of III-Nitrides on β-Ga2O3 and Its Vertical Structure LEDs

“…As mentioned above, the laser lift-off technique is one way to fabricate vertical structure LEDs, but will lead to additional defects and a rough surface to devices resulting from the high energy laser irradiation [40,41,42], while chemical lift-off will not damage the interface between epilayer and substrate [43]. Recently, researches have been carried out for chemical lift-off of GaN using various interlayers [43,44,45,46,47,48,106,107,114,115,116,117,118,119,120]. Lin et al demonstrated the CLO process of InGaN-based LEDs grown on triangle-shaped and truncated-triangle-striped patterned sapphire substrates employing AlN as a sacrificial layer [115,116].…”

“…However, using KOH as etchant might also damage the GaN grown on AlN. Horng et al reported the vertical structure nitride LED fabricated on Cu substrate via CLO process employing an AlN/strip-patterned-SiO 2 interlayer as a sacrificial layer [117]. In addition, the direct growth of GaN on CrN and ZnO has been demonstrated, and the CLO process to detach the GaN epilayer has been realized using CrN and ZnO as sacrificial layers [43,44,45,46,47,48].…”